I got the 1628SEA's last month. I had a chance to hook them up and run a frequency response test. I remember that the notch was gone, and the response was about 2 db down at 20 KHz. I am at work now, so I don't have the data. I have been so busy at work that I haven't had the time to post the data, or (worse) even listen to the amp. I have a new set of transformers, and I haven't touched the power switch in 3 weeks.
1628SEA Users - try this
Before you go killing yourself with 813's, try this out. It's
very easy and sounds really good. It's always in A2 mode.
New 811A's are maybe $13-17 bucks... You can use a 6V motorcycle battery or battery eliminator to light the filaments.
You can also use the 572B tube as well, if you have any handy.
http://world.std.com/~doyle/811Aiter1.jpg
-- Jim
Before you go killing yourself with 813's, try this out. It's
very easy and sounds really good. It's always in A2 mode.
New 811A's are maybe $13-17 bucks... You can use a 6V motorcycle battery or battery eliminator to light the filaments.
You can also use the 572B tube as well, if you have any handy.
http://world.std.com/~doyle/811Aiter1.jpg
-- Jim
OK, I have had the 1628SEA's for over a month, and they have been sitting on the shelf, staring at me.
A long shot at work (a high speed CMOS RF test chip) turned out to be very successful, which means that it must be tested 27 different ways and documented. I have had little time for audio lately. The audio time that I have is spent building and photographing SimpleSE boards for the assembly manual. This has left me with 4 completed boards and dozens of transformers to test.
Sherri is not home tonight, so I connected the 1628SEA's up to a fresh board in UL mode, hooked up a fat power transformer that gives me 465 volts of B+, put in a pair of the Shuguang Coke Bottle 6L6GC's and turned up the current until I reached a dull red glow, about 35 watts dissipation. I then ran frequency response curves with and without cathode feedback.
I have been listening to it all night. After about 2 hours of various music, I swapped in the old 1628SE's (5 minute job) and listened some more. After about 15 minutes, I pulled the plug, and put back the 1628SEA's. They have that "something" that just sounds right.
I will have a more detailed comparison between about 10 different types of popular OPT's when I get the time to finish it. I have to get my HP8903 fixed first.
Included below is the frequency response measured at 5 watts.
A long shot at work (a high speed CMOS RF test chip) turned out to be very successful, which means that it must be tested 27 different ways and documented. I have had little time for audio lately. The audio time that I have is spent building and photographing SimpleSE boards for the assembly manual. This has left me with 4 completed boards and dozens of transformers to test.
Sherri is not home tonight, so I connected the 1628SEA's up to a fresh board in UL mode, hooked up a fat power transformer that gives me 465 volts of B+, put in a pair of the Shuguang Coke Bottle 6L6GC's and turned up the current until I reached a dull red glow, about 35 watts dissipation. I then ran frequency response curves with and without cathode feedback.
I have been listening to it all night. After about 2 hours of various music, I swapped in the old 1628SE's (5 minute job) and listened some more. After about 15 minutes, I pulled the plug, and put back the 1628SEA's. They have that "something" that just sounds right.
I will have a more detailed comparison between about 10 different types of popular OPT's when I get the time to finish it. I have to get my HP8903 fixed first.
Included below is the frequency response measured at 5 watts.
Attachments
I guess that everyones definition of HiFi is a little bit different. Hammond claims +- 1 db from 30 Hz to 20 KHz (on both versions of the 1628). I would like to know how they measure this, and at what DC current.
I don't see it happening any time in the near future, but I plan on finishing my big transformer test web page sooner or later. I need to get my HP audio analyzer fixed to speed up the process of doing power sweeps. Once that happens, and I get all of this IC testing stuff done, I will set aside a rainy weekend for transformer testing. I plan to eventually sell all of the transformers that I bought for this testing (with amplifiers attached to them) so, I am motivated to finish it up.
In a perfect world, you get more or less what you pay for. If I recall correctly, the Hammond 1628SEA is about $99 if you shop carefully - if you want Tango response, you'll probably need to shell out Tango-type prices. That the cheaper transformers like the Hammonds and the Edcors perform as well as they do is a boon for the casual experimenter.
That leaves me out.
How about a transformer that claims 70 Hz to 18Khz, but tests out at 24Hz to 45KHz in the same amp as the Hammond 1628's at 8 watts. Oh, they cost $18 each! (the Edcor XSE15-8-5K) Granted these 1 1/2 pound monsters will saturate with bass signals that pass through the 1628's with ease. If I was building a low powered (2 watts or less) amp for use with efficient speakers using an 8 inch or smaller sized driver (limited bass below 60 Hz) the Edcors would be my transformer choice.
I am still deciding on which transformers will wind up in my own personal amps. If I had to choose now, I would take the 1628SEA's for the amp that goes in the living room to be used with my big speakers. The 15 inch driver can make good use of the serious wall shaking bass that these transformers (or the older 1628SE's) can provide. No other transformer that I tested could deliver the bottom that these could. (I had a $100 / transformer limit).
The amp that will be used in my work room requires more testing. For most listening the bass is limited by the speakers. The unusual impedance VS frequency curves of the Yamaha speakers makes measurements and calculations useless. Load lines assume a nice constant resistive load.
It is finally time to put one of my amplifiers into a pretty wooden box. I have the 1628SE's and the 1628SEA's in front of me now. They are exactly (within my measurement abilities) the same size. The hole pattern is 3 inches by 3.88 inches. The dimensions on Hammonds web site appear to be WRONG! Dimension "B" measures 4.90 inches to 4.95 inches (4 transformers). Dimension "E" measures 3.90 inches.
it doens't matter what 'fi' it measures at, the point is, how does it sound?
the thing about the small ones, is limited core size, and inductance, and no small tranny is going to have big power or bass, esp. cheap ones, most of those also coming from china, also I bet the cheap ones don't pay much attention to top end bandwidth, too
if you reckon on a 5x mark up which is typcial, the distributor taking around 40%, and the dealer the same, that leaves around $20 it takes hammond to make them.
these mark ups are roughly an industry standard, so, with the iron costing so little in a big hammond, you also have to ask why the other cheap ones cannot use similar amounts of iron.
finally, do you really think an extra layer or two costs as much as a load of iron?
the thing is, whilst you have to design to specifications mathematically, and of course its right to continuously improve that, the cheap ones, perhaps even the expensive ones, will not build 20 prototypes, and in audio as we know, there is no proven correlation yet between specifications and how good something sounds, so in audio
you do not always get what you pay for.
That's why you can't design in excellent sound, and why some cheap things sound excellent, and expensive ones can sound poor.
If you could design in excellent sound, everyone would be doing it, so clearly, they don't know how to.
question is, does a multi hundred $ transformer sound that much more worth it, against a hammond, that's the question you need ask
I have a number of output trannys, MQ, silk, james, diyhifisupply, amongst othersand am going to A/b them all, and reckon the most expensive will actually be very poor value indeed.
its a numbers game, the one man bands, and small makers, whilst maybe producing a handmade limited quantity thing, perhaps like a rolls royce, cannot produce to the same price as a hammond, who must make 10s of 1000s, but its not the same as a handmade work of art, sculpture, piece of carved wood, say, its just a bit of wound wire on a core, and machines do that very well indeed.
And of course, they have to artificially create a brand prestige by simply making up a figure in their head and asking for it.
if you like it, and prefer it, that's fine tho,
but don't, just cos its bespoke try to convince yourself, that you have paid $800 so it must sound good, as fools do with cables.
the thing about the small ones, is limited core size, and inductance, and no small tranny is going to have big power or bass, esp. cheap ones, most of those also coming from china, also I bet the cheap ones don't pay much attention to top end bandwidth, too
if you reckon on a 5x mark up which is typcial, the distributor taking around 40%, and the dealer the same, that leaves around $20 it takes hammond to make them.
these mark ups are roughly an industry standard, so, with the iron costing so little in a big hammond, you also have to ask why the other cheap ones cannot use similar amounts of iron.
finally, do you really think an extra layer or two costs as much as a load of iron?
the thing is, whilst you have to design to specifications mathematically, and of course its right to continuously improve that, the cheap ones, perhaps even the expensive ones, will not build 20 prototypes, and in audio as we know, there is no proven correlation yet between specifications and how good something sounds, so in audio
you do not always get what you pay for.
That's why you can't design in excellent sound, and why some cheap things sound excellent, and expensive ones can sound poor.
If you could design in excellent sound, everyone would be doing it, so clearly, they don't know how to.
question is, does a multi hundred $ transformer sound that much more worth it, against a hammond, that's the question you need ask
I have a number of output trannys, MQ, silk, james, diyhifisupply, amongst othersand am going to A/b them all, and reckon the most expensive will actually be very poor value indeed.
its a numbers game, the one man bands, and small makers, whilst maybe producing a handmade limited quantity thing, perhaps like a rolls royce, cannot produce to the same price as a hammond, who must make 10s of 1000s, but its not the same as a handmade work of art, sculpture, piece of carved wood, say, its just a bit of wound wire on a core, and machines do that very well indeed.
And of course, they have to artificially create a brand prestige by simply making up a figure in their head and asking for it.
if you like it, and prefer it, that's fine tho,
but don't, just cos its bespoke try to convince yourself, that you have paid $800 so it must sound good, as fools do with cables.
As with anything, sound quality is directly dependent on the ears and musical tastes of the listener. What sounds good to me will not appeal to someone with different musical tastes. The choice of speakers has an huge effect on the choice of OPT.
In my living room I have a pair of old (1941) Zenith console radios with modern (Silver Iris) 15 inch drivers installed. With these speakers wall shaking bass (down to about 30Hz) is a reality with a well designed SE amp. It is very easy to hear the difference on the lower frequencies between all of the different OPT's that I have tested. The Hammonds (1628SE and 1628SEA)win this contest by a large margin due to the amount of copper and iron present. I am presently designing and building an amplifier for use in that system and I have chosen the 1628SEA OPT's for it.
In my lab (very limited space) I use a pair of Yamaha NS10M studio near field monitors. These speakers have limited response below 65HZ. I can not hear much difference between the big Hammonds and any of the mid sized OPT's such as One Electron, Electra Print, and Transcendar. The deficiencies in the small transformers (Hammond 125CSE and Edcor XSE15-8-5K) are only obvious when cranked hard enough to saturate the core. I have not decided on the transformers for the newest amp for that system (I have 3 amps already), but it won't be the big Hammonds. Some of the smaller transformers have greater detail that the Hammonds do not have (the differences are small) and the bass response is wasted on those speakers.
I think that the 1628's (either ones) sound great in a system that can make use of their capabilities. The small Edcors and 125CSE's have their place too. I am sure that some of the "boutique" transformers have their place, and there are systems that will make use of their fine points. Based on what I have heard, I will probably try a pair of the James transformers when I have the funds.
I went to visit a friend who sells tubes on the way to visit my mom (a 700 mile trip). He offered me some "previously auditioned" tubes for $10 each. I purchased a few pairs of assorted power tubes.
I tested some of them in an amp that is currently under construction. Those who have listened to my previous rants know that was turned off by the early failure of several Sovtek 300B tubes. I got a pair of Electro Harmonix KT88's, because they were cheap, and because they had heat radiating fins welded to the plates.
The short story is that these tubes absoultely rocked. I cranked the dissipation up to 40 watts. There was no sign of death glow and the sound was great. I then went up to 45 watts and there was a faint glow on the plate of one tube with the room lights off.
There was a cool blue light show going on on the glass of the tubes. The 3 "D" shaped dots from the plate holes blink to the lead guitar, and the whole glass envelope pulses blue with heavy bass notes. I have never seen anything this bright before. Good sound, and a free light show, tomorrow morning, I am going to call up and purchase the remaining tubes.
I just had to post this picture.
I tested some of them in an amp that is currently under construction. Those who have listened to my previous rants know that was turned off by the early failure of several Sovtek 300B tubes. I got a pair of Electro Harmonix KT88's, because they were cheap, and because they had heat radiating fins welded to the plates.
The short story is that these tubes absoultely rocked. I cranked the dissipation up to 40 watts. There was no sign of death glow and the sound was great. I then went up to 45 watts and there was a faint glow on the plate of one tube with the room lights off.
There was a cool blue light show going on on the glass of the tubes. The 3 "D" shaped dots from the plate holes blink to the lead guitar, and the whole glass envelope pulses blue with heavy bass notes. I have never seen anything this bright before. Good sound, and a free light show, tomorrow morning, I am going to call up and purchase the remaining tubes.
I just had to post this picture.
